Association of the Robin sequence with the fragile X syndrome.

We report on 4 individuals with the fragile X [fra(X)] syndrome and the Robin sequence (or elements of that sequence). To our knowledge, this association has been described in only one other boy. However, males with the fra(X) syndrome have been reported to have an increased incidence of cleft palate. We recommend that children with a cleft palate or the Robin sequence be assessed for developmental delays and a family history of mental retardation. The fra(X) syndrome may be one of the genetic causes of the Robin sequence and, when indicated, children with the sequence should be tested for fra(X).     

Collagen XI sequence variations in nonsyndromic cleft palate,Robin sequence and micrognathia

Cleft palate is a common birth defect, but its etiopathogenesis is mostly unknown. Several studies have shown that cleft palate has a strong genetic component. Robin sequence consists of three of the following four findings: micrognathia, glossoptosis, obstructive apnea, and cleft palate. While cleft palate is mainly nonsyndromic, about 80 percent of Robin sequence cases are associated with syndromes. Mutations in genes coding for cartilage collagens II and XI, COL2A1, COL11A1 and COL11A2, have been shown to cause chondrodysplasias that are commonly associated with Robin sequence, micrognathia or cleft palate. We therefore analyzed a cohort of 24 patients with nonsyndromic Robin sequence, 17 with nonsyndromic cleft palate and 21 with nonsyndromic micrognathia for mutations in COL11A2. A total of 23 Robin sequence patients were also analyzed for mutations in COL2A1 and COL11A1. We detected two disease-associated mutations in patients with Robin sequence, an Arg to stop codon mutation in COL11A2 and a splicing mutation in COL11A1. Two putatively disease-associated sequence variations were found in COL11A1 in Robin sequence patients, one in COL11A2 in a patient with micrognathia and one in COL2A1 in two patients with Robin sequence. The results showed that sequence variations in these genes can play a role in the etiology of Robin sequence, cleft palate and micrognathia but are not common causes of these phenotypes.     

Three families with high expression of a fragile site at Xq27.3, lack of anomalies at the FMR-1 CpG island, and no clear phenotypic association.

We report on 3 families where the presence and segregation at high frequency of a fragile Xq27.3 site is not associated with the mutations and methylation anomalies typically seen in the fragile X [Fra(X)] syndrome. In one family, a folate insensitive fragile site was associated with Robin sequence in the propositus. In a second family a fra(X) negative mother has two fra(X) positive sons (one mentally retarded and the other newborn). The third family presents very high expression of a folate sensitive site, unlinked to mental retardation, and was described previously by Voelckel et al. [1989]. The fragile sites in these or similar families recently described must be different from the one associated with the fra(X) syndrome. Their association with a clinical phenotype or with mental retardation is certainly not consistent, and may represent an ascertainment bias. However, the relatively high frequency with which they have been found among previously diagnosed fra(X) families suggests that, at least in some cases, the association with mental impairment may be significant. In two families reported up to now, a male with high expression of such variant fra(X) site failed to transmit it to his daughter, which may reflect an imprinting effect. Previously diagnosed families should be reinvestigated before direct DNA analysis is used for prenatal or carrier diagnosis of the fra(X) syndrome.     

A new case of 2q duplication supports either a locus for orofacial clefting between markers D2S1897 and D2S2023 or a locus for cleft palate only on chromosome 2q13-q21

We report on a pure duplication of the proximal chromosome 2q in a 6.5-year-old boy with V-shaped midline cleft palate and bifid uvula, posteriorly located tongue, and micrognathia (Pierre Robin sequence), celiac disease, failure to thrive, and developmental delay. Cytogenetic and FISH analysis indicated a duplication of chromosome 2q13-q22. In general, pure proximal duplication or triplication of 2q is rare. The clinical features and chromosomal breakpoints of the 10 previously reported patients varied, and no common phenotype or proximal duplication/triplication 2q syndrome could be defined to date. However, based on four previous patients with different orofacial clefts and our case, a locus for orofacial clefting may be located at proximal 2q. The duplication/triplication comprised chromosome 2q13 in all five affected individuals including our patient. Our patient and three previous cases (two with cleft palate only (CPO) and one with cleft lip/palate (CL/P)) showed a cytogenetic breakpoint at 2q13, which could support the presence of a critical dominant gene disrupted by a common breakpoint, however, the fifth case with CPO showed different breakpoints, advocating against the disruption of a critical dominant gene and supporting that the overexpression of a gene(s) on chromosome 2q13-q21 may cause cleft palate only (CPO) and Pierre Robin sequence. Hence, our findings support either the presence of one locus for orofacial clefting (CL/P, CPO, and Pierre Robin sequence) between markers D2S1897 (chromosome 2q12.2) and D2S2023 (chromosome 2q14.2), or alternatively the presence of a locus for CPO and Pierre Robin sequence on chromosome 2q13-q21.     

Velo-cardio-facial syndrome and DiGeorge sequence with meningomyelocele and deletions of the 22q11 region

Approximately 5% of children with neural tube defects (NTDs) have a congenital heart defect and/or cleft lip and palate. The cause of isolated meningomyelocele, congenital heart defects, or cleft lip and palate has been largely thought to be multifactorial. However, chromosomal, teratogenic, and single gene causes of combinations of NTDs with congenital heart defects and/or cleft lip and palate have been reported. We report on 3 patients with meningomyelocele, congenital heart defects, and 22q11 deletions. Two of the children had the clinical diagnosis of velo-cardio-facial syndrome (VCFS); both also have bifid uvula. The third child had DiGeorge sequence (DGS). The association of NTDs with 22q11 deletions has not been reported previously. An accurate diagnosis of the 22q11 deletions is critical as this micro-deletion and its associated clinical problems is transmitted as an autosomal dominant trait due to the inheritance of the deletion-bearing chromosome. We recommend that all children with NTDs and congenital heart defects, with or without cleft palate, have cytogenetic and molecular studies performed to detect 22q11 deletions. © 1994 Wiley-Liss, Inc.     

Fragile X family with unusual digital and facial abnormalities, cleft lip and palate, and epilepsy.

We present a fragile X family with unusual clinical manifestations. These findings, which often occur in the X-linked FG syndrome, include minor limb anomalies, cleft lip and palate, characteristic facial appearance, gastrointestinal problems and epilepsy, and intellectual disability. In a total sample of 54 fra(X) families, the frequency of minor limb anomalies was estimated to be 32% in the affected males and 19% in the female heterozygotes. These anomalies tend to occur in several members of the same family, where some craniofacial abnormalities reported as characteristic of the FG syndrome have also been encountered. Possible mechanisms for the occurrence of these unusual manifestations in the fra(X) families are discussed.     

Fragile X family with unusual digital and facial abnormalities,cleft lip and palate,and epilepsy

We present a fragile X family with unusual clinical manifestations. These findings, which often occur in the X-linked FG syndrome, include minor limb anomalies, cleft lip and palate, characteristic facial appearance, gastrointestinal problems and epilepsy, and intellectual disability. In a total sample of 54 fra(X) families, the frequency of minor limb anomalies was estimated to be 32% in the affected males and 19% in the female heterozygotes. These anomalies tend to occur in several members of the same family, where some craniofacial abnormalities reported as characteristic of the FG syndrome have also been encountered. Possible mechanisms for the occurrence of these unusual manifestations in the fra(X) families are discussed. © 1992 Wiley-Liss, Inc.     

Designation of the TARP syndrome and linkage to Xp11.23-q13.3 without samples from affected patients

The Robin sequence is a well-known cause of cleft palate and can be sporadic or familial, isolated or syndromic. We present a four-generation family with a lethal disorder inherited in an X-linked recessive pattern that includes Talipes equinovarus, Atrial septal defect, Robin sequence, and Persistence of the left superior vena cava. We have designated this disorder "TARP" syndrome. All affected males die in infancy of unknown causes. An X-chromosome linkage scan was performed using 14 unaffected members of a single large family and 40 STRP markers. The gene was mapped to an 11-cM region in Xp11.23-q13.3. Markers DXS1003 and DXS8092 flank the region and three-point linkage analyses revealed a maximum LOD score of 2.75 at marker DXS1039. We have designated this locus as TARP. This locus was mapped without genotyping any affecteds and demonstrates that rare, lethal disorders can be evaluated by genetic linkage, even when no affected probands are available for study.     

Prenatal cytogenetic diagnosis of the fragile X syndrome in amniotic fluid: calculation of accuracy.

We have completed over 350 prenatal diagnoses for the fragile X [fra(X)] syndrome using amniotic fluid, chorion villus specimen (CVS), fetal blood sampling and molecular methods. A total of 300 amniotic fluid specimens have been received for prenatal diagnosis of the fra(X) syndrome. There was a documented family history of fra(X) in 170/300 amniotic fluid cases, and 23/170 were correctly identified as cytogenetically fra(X) positive (16 male; 7 female). Three males were false-negative, and one female was fra(X) negative but identified as a probable carrier by RFLPs. No fra(X) positive or false-negative results were found in the absence of a fra(X) family history. Because the a priori risk for the fra(X) syndrome for each pregnancy was different and widely variable, the determination of the accuracy of the prenatal diagnosis results requires a consideration of these variables. On this basis, the calculated accuracy of prenatal cytogenetic diagnosis for the fra(X) syndrome is approximately 97%. This accuracy can be improved further with the simultaneous use of molecular methods, especially in view of recent developments.     

Robin sequence without cleft palate: Genetic diagnoses and management implications

Robin sequence (RS), the triad of micrognathia, glossoptosis, and airway obstruction, is a major cause of respiratory distress and feeding difficulties in neonates. Robin sequence can be associated with other medical or developmental comorbidities in ~50% of cases (“syndromic” RS). As well, RS is variably associated with cleft palate (CP). Previous studies have not investigated differences in clinical characteristics of children with RS based on presence or absence of CP. We retrospectively reviewed 175 children with RS and compared genetic diagnoses, medical and developmental comorbidities, severity of airway obstruction, and feeding outcomes between those with and without CP. Strikingly, 45 of 45 (100%) children with RS without CP were classified as syndromic due to presence of comorbidities unrelated to RS, while 83 of 130 (64%) children with RS with CP were classified as syndromic. Among 128 children with syndromic RS, there were no differences in severity of airway obstruction, surgical intervention rate or type, or feeding outcome at 12 months based on CP status. Our findings support the conclusion that the pathogenesis of RS without CP is distinct from RS with CP and more likely to cause additional medical or developmental problems. Alternatively, children with RS without CP and without additional anomalies present may be under recognized.     

Carrier testing in the fragile X syndrome: Attitudes and opinions of obligate carriers

This study surveyed obligate carriers of the fragile X syndrome fra(X) to ascertain opinions and attitudes regarding carrier testing. Female carriers of fra(X) syndrome were recruited during their visits to the Fragile X Clinic at Duke University Medical Center. Twenty-eight obligate carriers completed a 48 question structured interview and a visual analog scale (VAS). Strong trends in the responses were identified. Fra(X) syndrome was viewed as a very serious problem and the risk to offspring high. Subjects reported that prior knowledge of carrier status would have changed their reproductive plans. All felt that relatives should be informed about the inheritance of fra(X) syndrome; the mean age given for preferred age to inform their children of the inheritance of fra(X) syndrome was 12 years, and mean age given for optimal timing of carrier testing was 10 years. The women interviewed indicated that growing up with knowledge of their carrier status would have been preferable to learning this information as adults and they endorsed an aggressive approach to informing and testing their children. Further investigation is warranted to determine the psychological consequences of carrier testing for fra(X) syndrome in order to develop appropriate guidelines for testing and informing individuals at risk for fra(X) syndrome. Am. J. Med. Genet 68:62–69, 1997 © 1997 Wiley-Liss, Inc.     

Methylation and mutation patterns in the fragile X syndrome.

Chromosomes carrying the mutation causing the fragile X [fra(X)] syndrome have been shown to have an unstable DNA sequence close to or within the fragile site. The length variation is located within a DNA fragment containing a CGG trinucleotide repeat which is unstable in both mitosis and meiosis. We have used the probe StB12.3 from the region to analyze the mutations and the methylation patterns in 21 families segregating for the fra(X) syndrome. Among 40 fra(X) males all showed an abnormal pattern. The normal 2.8 kb band was absent in 36 individuals and replaced by a heterogeneous smear of larger size. The remaining four were shown to be "mosaics" with the presence of both mutated, unmethylated and mutated, methylated fragments. We found four normal transmitting males, one which was a great-grandson of another normal transmitting male indicating that the pre-mutation can remain stable through two meioses in the female. In nine fra(X) positive females the abnormal pattern consisted of a smear, usually seen in affected males, in addition to the normal bands. Five of these females were mentally normal. Of clinical importance is the prediction of mental impairment in females. We suggest that this is not made by the detection of the full mutation alone, but rather by the degree of methylation of the normal X chromosome. Our results suggest that difference of clinical expression in monozygotic twins may be correlated with difference in methylation pattern. Six out of 33 fra(X) negative females at risk were diagnosed as carriers. Our observations indicate that molecular heterogeneity is responsible for variable expression of the fra(X) syndrome in both males and females.     

Short stature,Robin sequence,cleft mandible,pre/postaxial hand anomalies,and clubfoot: A new autosomal recessive syndrome

We report on 5 unrelated Brazilian children with short stature, Robin sequence, cleft mandible, pre/postaxial hand anomalies, and clubfoot. Genetic aspects and phenotypic manifestations are compared with those of previous reports of acrofacial dysostoses and with other Robin sequence syndromes. We suspect that these patients present a previously undescribed autosomal recessive syndrome.     

Short stature, Robin sequence, cleft mandible, pre/postaxial hand anomalies, and clubfoot: a new autosomal recessive syndrome.

We report on 5 unrelated Brazilian children with short stature, Robin sequence, cleft mandible, pre/postaxial hand anomalies, and clubfoot. Genetic aspects and phenotypic manifestations are compared with those of previous reports of acrofacial dysostoses and with other Robin sequence syndromes. We suspect that these patients present a previously undescribed autosomal recessive syndrome.     

Toriello-Carey syndrome with a 6Mb interstitial deletion at 22q12 detected by array CGH

Toriello-Carey syndrome is a rare multiple congenital anomaly syndrome comprising agenesis of the corpus callosum, telecanthus, short palpebral fissures, abnormal ears, Pierre Robin sequence, and cardiac anomaly. Autosomal recessive inheritance has been hypothesized and chromosome abnormalities have been reported. The present case is a girl with agenesis of the corpus callosum, a large cleft palate, telecanthus, hypertelorism, atrial septal defect, ventricular septal defect, and patent ductus arteriosus. A routine karyotype and fluorescence in situ hybridization subtelomeric analysis were normal. Array comparative genomic hybridization (CGH) identified a de novo 6 Mb interstitial deletion at 22q12.1→22q12.2. These findings support recent findings of chromosomal abnormalities in patients with the Toriello-Carey phenotype. We suggest that the clinical features described in some cases with Toriello-Carey syndrome might be due to cryptic chromosomal rearrangements and that array CGH should be considered in any case presenting with clinical features of Toriello-Carey.     

Metacarpophalangeal pattern profile analysis in fragile X syndrome

We analyzed the metacarpophalangeal pattern profile (MCPP) on 18 male individuals from 16 families with fragile X--fra (X), or Martin-Bell--syndrome and calculated a mean syndrome profile. Fourteen of 18 individuals with fra (X) syndrome had significant positive correlations which indicated clinical homogeneity. Discriminant analysis of individuals with fra (X) syndrome compared with a sample of normal individuals produced a correct classification rate of 88% based on a function of 3 MCPP variables that may provide a useful tool in screening individuals for the fra (X) syndrome. Discriminant and correlation analyses of individuals with Sotos sequence and individuals with fra (X) syndrome did not identify MCPP similarities. Therefore, there was no MCPP evidence in our study of patients with Sotos sequence and fra (X) chromosome expression.     

Resolving clinical diagnoses for syndromic cleft lip and/or palate phenotypes using whole‐exome sequencing

Individuals from three families ascertained in Bogota, Colombia, showing syndromic phenotypes, including cleft lip and/or palate, were exome‐sequenced. In each case, sequencing revealed the underlying causal variation confirming or establishing diagnoses. The findings include very rare and novel variants providing insights into genotype and phenotype relationships. These include the molecular diagnosis of an individual with Nager syndrome and a family exhibiting an atypical incontinentia pigmenti phenotype with a missense mutation in IKBKG. IKBKG mutations are typically associated with preterm male death, but this variant is associated with survival for 8–15 days. The third family exhibits unusual phenotypic features and the proband received a provisional diagnosis of Pierre Robin sequence (PRS). Affected individuals share a novel deleterious mutation in IRF6. Mutations in IRF6 cause Van der Woude and popliteal pterygium syndrome and contribute to nonsyndromic cleft lip phenotypes but have not previously been associated with a PRS phenotype. Exome sequencing followed by in silico screening to identify candidate causal variant(s), and functional assay in some cases offers a powerful route to establishing molecular diagnoses. This approach is invaluable for conditions showing phenotypic and/or genetic heterogeneity including cleft lip and/or palate phenotypes where many underlying causal genes have not been identified.     

Pontine hypoplasia in Carey-Fineman-Ziter (CFZ) syndrome

We describe an infant with multiple congenital anomalies including cleft palate and micrognathia, M?bius sequence, developmental delay, myopathy, hydronephrosis, and bilateral clubfeet. These features are consistent with Carey-Fineman-Ziter (CFZ) syndrome (MIM 254940), which has been previously reported in six children (including two sibling pairs). Cranial magnetic resonance imaging (MRI) revealed an unusually small pons, a finding not previously described in CFZ syndrome.     

Validation of linkage-based DNA-diagnosis of fragile X gene carriers with the CGG repeat probe.

We have evaluated our carrier testing for the fragile X [fra(X)] syndrome, which was based on linked DNA markers, with the direct analysis of the CGG repeat sequence in the fra(X) gene. PstI and EcoRI blots were hybridized with a probe derived from the region just 3' of the CGG repeat in Xq27.3. We found the mutation analysis to be very sensitive as all 71 obligate gene carriers as well as 135 fra(X) patients tested showed evidence for an increased restriction fragment length encompassing the CGG repeat sequence with or without dispersion of the hybridization signal (mosaicism). Based on linked DNA markers, 6 out of 50 cytogenetic negative and mentally normal males at risk and 15 of 72 females at risk had inherited the allele at risk. All of these diagnoses could be confirmed by analysis of the CGG repeat length.     

Individual variation and specific cognitive deficits in the fra(X) syndrome

Mental retardation has been associated with fra(X) but comprehensive psychological evaluation has rarely been applied to 2 major behavioral questions 1) the extent of individual variation in IQ among fra(X) males and the possibility of some fra(X) males being of normal IQ; and 2) whether there is a depression in general IQ or whether specific abilities are impaired. The problems of developing an effective battery of tests for assessing fra(X) are discussed. These questions were examined in 54 individuals, comprising fra(X) males, their obligate carrier mothers and those sisters shown to have the fra(X). Among noninstitutionalised males nonverbal IQ as measured on a Block Design test ranged from 100 to 0, and vocabulary scores while generally higher, ranged from 79-33. The males scored low on a digit span memory task, while performance on a memory of objects task was adequate. Despite lower overall scores, a similar pattern and variability emerged in institutionalised males. Daughters were extremely variable in performance and the mothers performed much better, supporting the view that women who have children are a selected subset of fra(X) syndrome individuals. The performance of one male is discussed in detail. His vocabulary and nonverbal IQ scores were normal, despite his having other specific cognitive deficits. The pattern of abilities and behavior seen in fra(X) may result in an overestimation of intelligence and underestimation of penetrance when based on clinical impressions rather than formal psychological assessment. The implications of this for molecular and for population genetic approaches to fra(X) are discussed.